Historically, refrigeration systems have used various fluorocarbons and hydrofluorocarbons as refrigerant fluids to generate refrigeration and to provide the refrigeration to a heat load. Recently the use of some such refrigerants has been questioned on environmental and other grounds. Systems which use an environmentally friendly working fluid, such as air, are known. However, such systems typically are less efficient than systems using the more conventional refrigerants. For example, air systems commonly have a pinch at the warm end of the heat exchanger used in the system which limits the refrigeration capacity of the system. This is particularly a problem when the provision of the refrigeration is desired at a very cold temperature.
Accordingly it is an object of this invention to provide an improved method for generating a cold gas for the provision of refrigeration.
It is another object of this invention to provide an improved method for generating a cold gas for the provision of refrigeration which employs an environmentally benign working fluid.
It is a further object of this invention to provide an improved method for generating a cold gas for the provision of refrigeration which employs an environmentally benign working fluid and can efficiently provide the refrigeration at a very cold temperature.